taken from www.tonina-forest.net
You can see more pics here.
For some info in english, go here
So far its called Plagiomnium trichomanes which has its emmersed form shown here
The taiwanese owner has been growing it submersed for over a year, so no problems there. T<28 celsius and nutrient rich water preferred. The plant is described to grow into a round ball-like bush with no real roots. Hard to propagate, hard to find.